Objective:To study the chemical constituents of 95% ethanol extract of the whole plant of Elephantopus scaber and investigate its antioxidant activity. Method:The chemical constituents were isolated and purified by silica gel column chromatography,Sephadex LH-20 column chromatography,ODS column chromatography,semi-preparative high performance liquid chromatography (HPLC) and recrystallization methods,while their structures were identified on the basis of nuclear magnetic resonance (NMR), mass spectrometry and comparison of their spectral data with those reported in the literature. Result:Fourteen compounds were isolated and their structures were identified as:(E)-3-(3,4-dihydroxybenzylidene)-5-(3,4-dihydroxyphenyl)-2(3H)-furanone (1),esculetin (2),dihydrosyringenin (3),(+)-isololiolide (4),caffic acid (5),luteolin-7-O-β-D-glucuronide (6),luteolin-7-O-β-D-glucuronide methyl ester (7),chlorogenic acid methyl ester (8),blumenol A (9),(6R,9R)-3-oxo-α-ionol-β-D-glucopyranoside (10),byzantionoside B (11),3,5-O-dicaffeoyl quinic acid methyl ester (12),3,4-O-dicaffeoyl quinic acid methyl ester (13) and 4,5-O-dicaffeoyl quinic acid methyl ester (14). Conclusion:Compounds 1-4 and 8-10 were isolated from the genus Elephantopus for the first time. Compound 11 was isolated from E. scaber for the first time. The DPPH radical and ABTS⁺ radical scavenging experiments on twelve of these compounds showed that compounds 1,2,5,6,12 and 13 had significant antioxidant activity.